The term “flexible cable,” as used herein, means any flexible, elongated, energy or fluid-conducting device, such as a cable composed of one or more electrical wires or optical fibers, a fluid-conducting hose for conducting compressed air or a hydraulic fluid used as a medium for transmission of motive power, a flexible conduit used to convey a gas, a liquid, or another fluid material for use in a machine or industrial process, a flexible actuator such as a Bowden wire, or a flexible rotating shaft with or without a non-rotating sheath. Such flexible cables are used, for example, to connect relatively moving parts of a machine such as a machine tool, an industrial robot, or a conveyor or other material-handling or material-carrying machine, such as a hoist or other machine used in a civil engineering application.
When a flexible cable is connected to a moving part, torsion, flexion, and tensile forces applied to the cable as a result of movement of the moving part can result in damage to, or distortion of, the cable, and interfere with smooth movement of the cable and of components connected to the cable. Cable guides have been used to avoid damage and distortion of the cables, and to promote smooth movement.
A typical cable guide G is shown in FIG. 6. The guide is composed of a plurality of flexibly interconnected links forming an elongated channel though which a cable C extends. The guide, which has a fixed end part G1, a movable end part G5, and an intermediate folded part G3, is configured so that a lower part G2 of the guide is in mutually facing, opposed, relationship to an upper part G4 of the guide. The particular links which constitute the folded part G3, of course, depend on the relationship between the upper part and the lower part.
Each of the links of the cable guide comprises a pair of side plates Ga disposed on opposite sides of the cable C and a pair of connecting elements Gb, bridging the side plates, one plate Gb of each link being on the outer side of the cable, i.e. on the top side of the upper part, the bottom side of the lower part or the outer side of the folded part. The side plates are hinged to one another so that the guide can bend at least in a single plane, and, preferably, the side plates are configured to limit flexion of the guide to a specific minimum radius of curvature in order to avoid kinking of the cable C.
Where a cable guide of sufficient length is folded on itself, it is possible for two portions of the guide to come into face-to-face contact with each other. Friction between the contacting parts of the guide can obstruct smooth reciprocating motion. Moreover, frictional contact over time can cause wear and eventual breakage of the cable guide. Breakage can also result from interference between projecting portions of the two facing parts of the guide.
Skate trucks, such as skate truck 400 in FIG. 7, have been used to avoid contact between the mutually facing parts of a folded cable guide. The skate truck 400 of FIG. 4 is sandwiched between the lower parts G2 and the upper parts G4 of two cable guides. A typical skate truck is described in United States Patent Application Publication No. 2005/0155337, published on Jul. 21, 2005.
The conventional skate truck 400 of FIG. 7 is composed of a number of connected skate units 410, as shown in FIG. 8. Each skate unit 410 includes four rollers 412, sandwiched between upper and lower parts of the cable guide, a first pair of rollers being rotatably mounted disposed on a left frame member 413 on one side of the skate unit and a second pair of rollers being rotatably mounted on a right frame member 413 on the opposite side of the skate unit. Connecting blocks 414, which join the adjacent truck units in series, keep the right and left frame members 413 at the required spacing from each other. As shown in FIG. 8, the frame members 413 are rigidly secured to the connecting blocks by bolts 415, which are threaded into threaded holes in the connecting blocks.
Since the adjacent skate units 410 are rigidly secured to the connecting blocks by bolts 415, the skate truck is unable to adapt to flexion of the cable guide in the vertical direction. Nor is it able to adapt to snaking movement of the cable guide in horizontal directions transverse to the direction of advancing movement of the skate truck. Thus, when horizontal or vertical flexion of the cable guide occurs, excessive force can be generated in the skate units 410, resulting in deformation or damage to the cable guide.
Accordingly, an object of this invention is to provide a skate truck having flexibility, enabling it to adapt smoothly to vertical movements of a cable guide as well as to lateral horizontal movement of the cable guide relative to the direction of movement of the skate truck.